HA Migration (not live) Howto for an Active/Active Xen system using DRBD:

So what does all this produce? Node 1 has N DomUs and so does Node 2. Each set of DomUs is on its own drbd device and each node is primary for one of these devices. When a node fails, heartbeat sets the other node as primary for the affected drbd device, activates the LVM VG and LVs and starts the affected set of DomUs via their custom xendomains script (xd1 or xd2). It works great. I’ve rebooted, pulled the plug, and hit the power button and everything fails over OK. There’s a slight delay of about 90 seconds since it isn’t live migration but my environment can tolerate this.